Magnetic tape cartridge for housing a reel

ABSTRACT

A single reel with magnetic tape wound thereon is housed in a case. A restraining member, for restricting rotation of the reel by moving toward or away from the reel, is urged in a restraining direction by an urging member. The pushing-up portions of a releasing member are inserted into the through holes bored in the reel gear of the reel  2  so that the lower ends can abut a driving gear. The releasing member moves the restraining member in a releasing direction by moving according to the chucking operation of drive-side rotation drive means. In this manner, reel-rotation restraining means allows rotation of the reel when being used and restricts the rotation when not being used. In this construction, each of the through holes is bored between the tooth edges of the reel gear so that the releasing member can perform a reliable releasing operation.

This is a divisional of application Ser. No. 09/701,971, filed Dec. 6,2000, which was the National Stage of International ApplicationPCT/JP99/02963, filed Jun. 3, 1999; the disclosure of which isincorporated herein by reference.

TECHINICAL FIELD

The invention relates to a magnetic tape cartridge and more particularlyrelates, in a magnetic tape cartridge for rotatably housing within acartridge case a single reel having magnetic tape wound thereon, to thestructure of reel-rotation restraining means for causing the reel to bein a rotation-restrained state when not being used.

BACKGROUND ART

In conventional tape cartridges used as storage media that are employedin external storage units for computers, etc., there is known a type inwhich magnetic tape is wound on a single reel and this reel is rotatablyhoused within a cartridge case. This magnetic tape is employed as a datastoring tape for computers, etc., and because important information isstored, reel-rotation restraining means to restrict rotation of the reelis installed so that problems, such as tape jamming, etc., do not occurand so that the magnetic tape is not forwarded unexpectedly when notbeing used, such as when being archived, etc.

The reel-rotation restraining means is equipped with a restrainingmember that restricts rotation of the reel by engaging part of the reel,and is provided so that when the cartridge is loaded into a drive unitsuch as an external storage unit, etc., a restrained state by therestraining member is released according to a reel chucking operationperformed by drive-side rotation drive means.

Hence, due to demands for enhancement in the reliability of theaforementioned operation of the reel-rotation restraining means,prevention of dust entry into the cartridge, etc., this reel-rotationrestraining means is provided in a structure separated into arestraining member for restricting rotation of the reel, an urgingmember for urging this restraining member in a restraining direction,and a releasing member for moving the restraining member in a releasingdirection by moving in accordance with the chucking operation of thedrive-side rotation drive means.

That is, in the non-operative condition, the reel is restricted by therestraining member so that it does not rotate unexpectedly, as a resultof which the magnetic tape is not forwarded. However, if the cartridgeis loaded into a drive unit and chucking of the reel is performed byrotation drive means, the releasing member moves in interlock with thechucking operation and releases the restraining member. In this state,the reel is rotatable and therefore the magnetic tape can be forwardedand rewound.

In the aforementioned mechanism, it is also preferable to perform thepushing operation, for the releasing movement of the releasing memberwhich results from the chucking operation of the drive-side rotationdrive means, at a plurality of positions on the outer peripheral portionrather than at a single position on the center portion, because a stablereleasing operation can thus be performed. At this time, it isadvantageous in achieving structural simplification, etc., to provide areel gear, which meshes the driving gear of the drive-side rotationdrive means, in the reel, to provide pushing-up portions, formed in partof the releasing member, so that the distal ends abut the driving gearthrough the through holes provided in the real gear, and to provide thedriving gear so that when the drive-side rotation drive means performsthe chucking operation, the driving gear pushes the pushing-up portionsand releases the releasing member.

However, piercing the reel gear and boring the through holes, asdescribed above, will reduce the mesh between the reel gear and thedriving gear and therefore become a problem with respect to driving thereel reliably. If the through hole is reduced from such a respect, theshape of the portion of the releasing member inserted into this throughhole will also become smaller and therefore there is a possibility thatit will become unstable for the tooth edge of the driving gear to abutthe reduced portion accurately and give a reliable pushing operation.

In addition, in the case where the pushing-up portions are formed inpart of the releasing member and are inserted into the through holes ofthe reel and slid, as described above, the releasing member is subjectedto the urging force of the urging member and gives rise to bendingdeformation. As a result, since a tilting force acts on the push-upportion, part of the outside surface is pushed against the inner surfaceof the through hole and the friction resistance becomes greater, thesliding between the pushing-up portion and the through hole isdisturbed, and there is a possibility that the releasing member will notbe able to release the restraining member reliably.

The present invention has been made in view of the above-mentionedpoints, and accordingly, the object of the invention is to provide amagnetic tape cartridge in which the releasing member of thereel-rotation restraining means is capable of performing a reliablereleasing operation.

DISCLOSURE OF THE INVENTION

To solve the aforementioned problems, there is provided a magnetic tapecartridge, for rotatably housing within a cartridge case a single reelhaving magnetic tape wound thereon, comprising reel-rotation restrainingmeans for allowing rotation of the reel when being used and restrictingthe rotation when not being used; wherein

the reel-rotation restraining means has a restraining member forrestricting rotation of the reel by moving toward or away from the reel,an urging member for urging the restraining member in a restrainingdirection, and a releasing member for moving the restraining member in areleasing direction, by rotating integrally with the reel and movingaccording to chucking operation of drive-side rotation drive means;

the reel is provided with a reel gear which meshes a driving gear of thedrive-side rotation drive means, and a pushing-up portion formed in partof the releasing member is provided so that a distal end thereof canabut the driving gear through a through hole provided in the reel gear;and

the through hole is bored between tooth edges of the reel gear.

Also, it is preferable that a recess engageable with a tooth edge of thedriving gear be formed in a distal end surface of the releasing memberwhich abuts the driving gear.

According to a magnetic tape cartridge such as the aforementioned, thethrough hole which is provided in the reel gear of the reel-rotationrestraining means is formed between the tooth edges of the reel gear.Therefore, even if the through hole is small, the tooth edge of thedriving gear which meshes the reel gear can reliably abut the pushing-upportion of the releasing member projecting through the through hole andpush the pushing-up portion. Since the movement of the releasing membercan be stably performed, the restraining member can be reliably releasedwith a predetermined amount of movement, and the operational reliabilityof the reel-rotation restraining means can be assured.

In addition, in another magnetic tape cartridge of the presentinvention, the reel is provided with a reel gear which meshes thedriving gear of the drive-side rotation drive means, and a pushing-upportion formed in part of the releasing member is provided so that adistal end thereof can abut the driving gear through a through holeprovided in the reel gear. The pushing-up portion and the through holeare brought into contact with each other through small protrusions whichreduce the contact area.

According to a magnetic tape cartridge such as the aforementioned, thepushing-up portion provided in the releasing member of the reel-rotationrestraining means, and the through hole provided in the reel, arebrought into contact with each other through small protrusions whichreduce the contact area. As a result, the friction resistance betweenthe two is reduced, and even if bending deformation develops in thereleasing member, movement of the pushing-up portions can be stablyperformed according to the chucking operation of the drive-side rotationdrive means. In addition, the restraining member can be reliablyreleased with a predetermined amount of movement, and movement to therestrained state can also be assured. Thus, the operational reliabilityof the reel-rotation restraining means can be assured.

In a preferred form of the magnetic tape cartridge, the opposite toothedges of the reel gear between which the through hole is bored areremoved so that they become flat shapes, curved surface shapes, orchambered surface shapes.

Another magnetic tape cartridge is characterized in that the releasingmember is formed by pressing of a metal sheet.

Still another magnetic tape cartridge is characterized in that the reelis provided with a guide member which guides part of the releasingmember in an inserting direction when inserting the pushing-up portionof the releasing member into the through hole.

A further magnetic tape cartridge is characterized in that thepushing-up portion of the releasing member is provided near each vertexof a generally triangular plate base. In a preferred form of thismagnetic tape cartridge, the plate base of the releasing member isformed integrally with the pushing-up portion with high-rigidity resinmaterial, while a sliding-contact portion, formed with a separate memberhaving a low friction characteristic, is rigidly attached integrally toa center portion of an upper surface of the base which comes intocontact with a center portion of a lower surface of the restrainingmember.

Another magnetic tape cartridge is characterized in that gate traces forinjection molding are provided near centers of rotation of therestraining member and the releasing member. In a preferred form of thismagnetic tape cartridge, in the releasing member which has thepushing-up portion and is formed by injection molding, such a bore whichreduces a wall thickness of the pushing-up portion is formed in theinterior of the pushing-up portion.

Still another magnetic tape cartridge is characterized in that the reelgear is driven to rotate in mesh with a driving gear in which a toothedge portion thereof is formed into a curved surface.

A further magnetic tape cartridge is characterized in that a tooth edgeportion of the reel gear is formed into a curved surface.

Another magnetic tape cartridge is characterized in that the reel isformed by molding a metal reel plate on a bottom surface thereof byinsert molding, and the reel is molded by a metal mold in which a holdmember for holding an inner peripheral surface of the reel plate isdisposed on an outer periphery of a gate.

Still another magnetic tape cartridge is characterized in that the reelis formed by molding a metal reel plate on the inner peripheral side ofthe reel gear by insert molding, and the reel is molded by a metal moldprovided with a means of preventing interference between a gear-portionmetal mold for molding the reel gear and the reel plate.

A further magnetic tape cartridge is characterized in that the reel isformed by molding a metal reel plate by insert molding and in that thereel is formed so that outside the outer peripheral surface of the reelplate, a clearance in the form of a circumferential groove is formedbetween the outer peripheral surface and a bottom wall of the reel, andso that outside the clearance, the reel gear is formed.

Another magnetic tape cartridge is characterized in that the reel isformed by molding a metal reel plate by insert molding and in that thereel is formed so that a reinforcement rib is formed on a surface of thereel plate which contacts a bottom wall of the reel.

Still another magnetic tape cartridge is characterized in that the reelis formed by molding a metal reel plate by insert molding and in thatthe reel is formed so that a recess is formed in a bottom wall of thereel which the reel plate contacts.

A further magnetic tape cartridge is characterized in that the reel isformed by joining a reel hub and an upper flange portion by adhesion,and in that the reel is formed so that the upper flange portion isprovided with a collar portion which fits onto an inner peripheralsurface of the reel hub, an annular protruding portion is formed betweenthe collar portion and a surface of the upper flange portion, and sothat an end surface of the annular protruding portion and an outerperipheral surface of the collar portion are adhered to the reel hub asadhesion surfaces.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front sectional view of a magnetic tape cartridge of anembodiment of the present invention in the non-operative condition;

FIG. 2 is an exploded perspective view of the essential parts of themagnetic tape cartridge of FIG. 1;

FIG. 3 is a sectional view of the essential parts of the magnetic tapecartridge of FIG. 1 in the operative condition;

FIG. 4 is a vertical sectional view of the essential parts of thethrough hole of the reel and the pushing-up portion of the releasingmember in FIG. 1;

FIG. 5A is a sectional view showing the essential parts of anotherembodiment of the pushing-up portion of the releasing member before achucking operation;

FIG. 5B is a sectional view showing the essential parts of FIG. 5 afterthe chucking operation;

FIG. 6 is a sectional view showing the essential part of anotherembodiment of the reel gear;

FIG. 7 is a perspective view showing another embodiment of the releasingmember;

FIG. 8 is a perspective view showing still another embodiment of thereleasing member;

FIG. 9A is a cross sectional view showing another embodiment of thethrough hole of the reel and the pushing-up portion of the releasingmember;

FIG. 9B is a cross sectional view showing still another embodiment ofthe through hole of the reel and the pushing-up portion of the releasingmember;

FIG. 10A is a cross sectional view showing a further embodiment of thethrough hole of the reel and the pushing-up portion of the releasingmember;

FIG. 10B is a cross sectional view showing a further embodiment of thethrough hole of the reel and the pushing-up portion of the releasingmember;

FIG. 11 is a front sectional view of a magnetic tape cartridge ofanother embodiment in the non-operative condition;

FIG. 12 is an exploded perspective view of the essential parts of themagnetic tape cartridge of FIG. 11;

FIG. 13 is a sectional view of the essential parts of the magnetic tapecartridge of FIG. 11 in the operative condition;

FIG. 14 is a sectional plan view showing the assembled state of the reeland releasing member of FIG. 11;

FIG. 15 is an enlarged part-plan view of the reel of FIG. 11;

FIG. 16 is a sectional view of the essential parts of the reel andreleasing member of FIG. 11;

FIG. 17 is a front sectional view of a magnetic tape cartridge of stillanother embodiment in the non-operative condition;

FIG. 18 is an exploded perspective view of the essential parts of themagnetic tape cartridge of FIG. 17;

FIG. 19 is a sectional view of the essential parts of the magnetic tapecartridge of FIG. 17 in the operative condition;

FIG. 20 is a plan view of the essential parts cut between the uppersurface of the releasing member and the lower surface of the restrainingmember in FIG. 19;

FIG. 21 is an enlarged sectional view of the center portion of thereleasing member;

FIG. 22 is an enlarged sectional view of the center portion of thereleasing member in another embodiment;

FIG. 23 is a front sectional view of a magnetic tape cartridge of afurther embodiment in the non-operative condition;

FIG. 24 is an exploded perspective view of the essential parts of themagnetic tape cartridge of FIG. 23;

FIG. 25 is a sectional view of the essential parts of the magnetic tapecartridge of FIG. 23 in the operative condition;

FIG. 26A is a sectional view showing an injection-molded state of therestraining member;

FIG. 26B is an enlarged view of the portion A in FIG. 26A;

FIG. 27A is a sectional view showing an injection-molded state of thereleasing member;

FIG. 27B is an enlarged view of the portion B in FIG. 27A;

FIG. 28 is a sectional view showing another injection-molded state ofthe releasing member;

FIG. 29 is a front sectional view of a magnetic tape cartridge of afurther embodiment in the non-operative condition;

FIG. 30 is an exploded perspective view of the essential parts of themagnetic tape cartridge of FIG. 29;

FIG. 31 is a sectional view of the essential parts of the magnetic tapecartridge of FIG. 29 in the operative condition;

FIG. 32 is a plan view of the essential parts cut between the uppersurface of the releasing member and the lower surface of the restrainingmember in FIG. 31;

FIG. 33 is a side sectional view showing the essential parts of a rigidattachment structure of the pushing-up portion of the releasing member;

FIG. 34A is a side sectional view showing the essential parts of anotherrigid attachment structure of the pushing-up portion of the releasingmember;

FIG. 34B is a side sectional view showing the essential parts of stillanother rigid attachment structure of the pushing-up portion of thereleasing member;

FIG. 35 is a sectional view showing the lower end portion of thepushing-up portion of a releasing member in another embodiment;

FIG. 36 is a plan view of the essential part of a driving gear;

FIG. 37A is a perspective view showing an example of the tooth edgeshape of FIG. 36;

FIG. 37B is a perspective view showing another example of the tooth edgeshape of FIG. 36;

FIG. 38 is a bottom view of the essential portion of a reel gear;

FIG. 39 is a front sectional view of the essential portion of the reelgear;

FIG. 40A is a bottom view of the essential part of a reel in anotherembodiment;

FIG. 40B is a sectional view of the injection-molded state of the reelshown in FIG. 40A;

FIG. 41A is a bottom view of the essential part of a reel in stillanother embodiment;

FIG. 41B is a sectional view of the injection-molded state of the reelshown in FIG. 41A;

FIG. 42 is a sectional view of an injection-molded state showing anotherembodiment of the structure for locking a reel plate;

FIG. 43 is a sectional view of an injection-molded state showing stillanother embodiment of the structure for locking a reel plate;

FIG. 44A is a front view showing another embodiment of the reel plate;

FIG. 44B is a sectional view of FIG. 44A;

FIG. 44C is another sectional view of FIG. 44A;

FIG. 45A is a front view showing still another embodiment of the reelplate;

FIG. 45B is a sectional view of FIG. 45A;

FIG. 46A is a front view showing another embodiment of the reel plate;

FIG. 46B is a sectional view of FIG. 46A;

FIG. 47A is a front view showing still another embodiment of the reelplate;

FIG. 47B is a sectional view of FIG. 47A;

FIG. 48A is a front view showing another embodiment of the reel plate;

FIG. 48B is a sectional view of FIG. 48A;

FIG. 49 is a sectional view showing another form of the reel plate andthe reel gear;

FIG. 50 is a sectional view showing still another form of the reel plateand the reel gear;

FIG. 51 is a sectional view showing a further form of the reel plate andthe reel gear;

FIG. 52 is a sectional view showing a further form of the reel plate andthe reel gear;

FIG. 53A is a bottom view of the essential part of a reel in anotherembodiment;

FIG. 53B is a sectional view of the injection-molded state of the reelshown in FIG. 53A;

FIG. 54 is a plan view showing another embodiment of the reel plate;

FIG. 55 is a plan view showing another embodiment of the reel;

FIG. 56 is a sectional view of a reel according to still anotherembodiment;

FIG. 57 is an enlarged view of the essential part of the reel of FIG.56; and

FIG. 58 is a sectional view of a reel according to a further embodiment;and

FIG. 59 is an enlarged view of the essential part of the reel of FIG.58.

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention will hereinafter be described in detail, based onembodiments shown in the drawings. FIG. 1 is a sectional view of amagnetic tape cartridge of an embodiment in the non-operative condition,FIG. 2 an exploded perspective view of the essential parts, and FIG. 3asectional view of the essential parts in the operative condition.

The magnetic cartridge 1 is constructed so that magnetic tape (notshown) is wound on a single reel 2 and that the reel 2 is housedrotatably within a cartridge case 3. The cartridge case 3 is formed byfastening an upper case 31 and a lower case 32, which is provided at acenter portion thereof with an opening 32 a, together with vis screws,etc. The magnetic tape cartridge 1 is also equipped with reel-rotationrestraining means 10 for allowing rotation of the reel 2 when beingused, and restricting the rotation when not being used.

The reel 2 consists of a bottomed cylindrical reel hub 21, in whichmagnetic tape is wound on the outer periphery, and upper and lowerflange portions 22 and 23 respectively projected in disk form in theradial direction from the upper and lower ends of the outer periphery ofthis reel hub 21. The reel hub 21 and the lower flange portion 22 areintegrally formed from synthetic resin and are united with the upperflange portion 23, for example, by ultrasonic welding. The reel hub 21is closed at a lower portion thereof by a bottom wall 21 a. A reel gear24, for driving the reel 2 to rotate, is provided in annular form in theradially outer portion of the lower surface of the bottom wall 21 a. Areal plate 25 for magnetic suction, formed from an annular metal plate,is attached on the radially inner side from this reel gear 24. And thereel gear 24 and reel plate 25 of the reel 2 are disposed to face anopening 32 a in the bottom surface of the cartridge case 3. Note thatthe reel 2 is urged downward by an urging member 5 to be describedlater.

In addition, driving-side rotation drive means 11 is equipped on theupper end face of a rotating shaft 12 with a driving gear 13 and amagnet (not shown). With the chucking operation of the drive means 11,the magnetic tape cartridge 1 loaded into a bucket (not shown) on thedriving side is lowered to the rotating shaft 12. The driving gear 13meshes the reel gear 24, and the reel plate 25 is attracted by themagnet, whereby the meshed state is held.

Next, the mechanism of the reel-rotation restraining means 10 will bedescribed. This reel-rotation restraining means 10 has a restrainingmember 4 movable toward or away from the reel 2 in an up-and-downdirection, the urging member 5 for urging the restraining member 4 in arestraining direction, and a releasing member 6 (synthetic resin moldedproduct) for moving the restraining member in a releasing direction.

3 (three) through holes 26 penetrating the reel gear 24 in theup-and-down direction are disposed in the bottom wall 21 a of the reel 2at regular intervals on a circle. Furthermore, 3 (three) stopperprotrusions 27 are stood up in the upper surface of the bottom wall 21 aat regular intervals on a circle at positions different in phase fromthe through holes 26, the upper end of each stopper protrusion 27 beingformed into a gear tooth shape. Note that three or more through holes 26and three or more stopper protrusions 27 may be disposed, and the upperend of the stopper protrusion 27 may be formed into a plurality of gearteeth. In the reel 2 shown in FIG. 2, only the part of the bottom wall21 a cut away from the reel 2 is shown.

On the restraining member 4, a disc portion 41 thereof is disposedwithin the reel hub 21 of the reel 2, facing the bottom wall 21 a. Arestraining gear 42 is formed in annular form in the radially outerportion of the lower surface of the disc portion 41 and is meshable withthe upper ends of the stopper protrusions 27. In addition, the centerportion of the lower surface of the disc portion 41 is projected into aconvex shape and contacts the center portion of the upper surface of thedisc portion 61 of the releasing member 6 that is to be described later.

Furthermore, a protruding portion 44 is formed on the upper surface ofthe disc portion of the restraining member 4 so that it extends upward.This protruding portion 44 is provided with a stopper groove 45 in theform of a cross, extending in the up-and-down direction. On the otherhand, a swivel stopping protrusion 33 which is inserted into the stoppergroove 45 is stood up in the inner surface of the upper case 31 of thecartridge case 3. Also, with the engagement between the stopper groove45 and the swivel stopping protrusion 33, the restraining member 4 isdisposed so as to be movable in the up-and-down direction withoutrotating. Note that the stopper groove 45 and the swivel stoppingprotrusion 33 may be provided in the form of a straight line. Also, theswivel stopping protrusion may be formed in the restraining member 4,and the stopper groove may be formed in the upper case 31.

The urging member 5 such as a coil spring is compressedly interposedbetween the upper surface of the disc portion 41 on the radially outerside from the protruding portion 44 and the inner surface on theradially outer side of the swivel stopping protrusion 33, whereby therestraining member 4 is urged downward in the restraining directionwhere the restraining gear 43 and the stopper protrusion 27 engage eachother.

In addition, the releasing member 6 is interposed between therestraining member 4 and the bottom wall 21 a of the reel hub 21 so thatit is movable up and down. At three positions on the radially outerportion of the disc portion 61 on the central side, arm portions 62 areformed to extend in the radial direction. The arm portions 62 areprovided on the outer lower surface with pushing-up portions 63 in theform of a square bar extending in the up-and-down direction,respectively. The pushing-up portions 63 are inserted into the throughholes 26 bored in the reel hub 21 so that they are movable into and outof the through holes 26, respectively. The lower ends of the pushing-upportions 63 are located facing the tooth portion of the reel gear 24 ofthe lower surface of the reel hub 21. At this time, each of the stopperprotrusions 27 is located between two adjacent arm portions 62. Notethat the pushing-up portion 63 may be formed into a round bar shape.

At the lower most position of the releasing member 6 (FIG. 1), the lowerend face of the pushing portion 63 is at approximately the tooth edgeposition of the reel gear. As the driving gear 13 is meshed with thereel gear 24 by the chucking operation of the drive-side rotation drivemeans 11, the releasing member 6 is pressed and is pushed up by apredetermined amount of stroke (FIG. 3). Also, if it is fitted into thethrough holes 26 of the pushing-up portion 63, this releasing member 6rotates integrally with the reel 2. In addition, the lower end of thecentral convex portion of the lower surface of the restraining member 4is urged to abut the upper surface of the releasing member 6 by theurging member 5, and both make sliding contact with each other.

The through hole 26 formed in the reel gear 24 of the reel 2 is boredbetween adjacent tooth edges 24 a of the reel gear 24 so that it has awidth of one pitch, as shown in FIG. 4. That is, it is bored so that thecenter of the pushing-up portion 63 of the releasing member 6 insertedinto this through hole 26 becomes the center of the tooth groove andcoincides with the tooth edge of the driving gear 13 which meshes withthis reel gear 24.

The opening width of the through hole 26 is provided so that it is aboutone pitch or two pitches of the real gear 24.

Note that at least either the restraining member 4 or the releasingmember 6 may be formed with synthetic resin containing a lubricant suchas molybdenum disulfide, polytetrafluoroethlene, graphite, potassiumtitanate whisker, silicon (various grades of dimethylpolysiloxane andthe degenerated substances), etc., whereby the lubrication may beimproved. Also, along with the above-mentioned lubricant, a lubricant,such as an oleic acid amide lubricant, an erucic acid lubricant, astearic acid amide lubricant, a bisfatty acid amide lubricant, a non-ioninterfacial active lubricant, a hydrocarbon lubricant, a fatty acidamide lubricant, an ester lubricant, an alcohol lubricant, a metallicsoap, etc., may be doped. Furthermore, it is preferable that syntheticresin employ polycarbonate (PC), polyoxymethylene (POM), acrylonitrilebutadiene styrene (ABS) containing glass fiber, polyphenylenesulfide(PPS), aliphatic polyamide such as nylon 6 or nylon 66, aromaticpolyamide, ultra high polymer polyethylene, isotactic polypropylene,syndiotactic polystyrene, and wear-resisting resin with an imide group,such as polyimide, polyamideimide, polyetherimide, etc. This reduces thefriction and wear between the sliding-contact portions of both, andbecause of a reduction in the driving resistance, the reel 2 can bestably rotated. In addition, the occurrence of powder due to wear issuppressed, whereby the reliability of recording and reproducingperformances can be assured.

The operation of the reel-rotation restraining means 10 will bedescribed. FIG. 1 shows a non-operative condition, such as an archivedcondition, etc., of the magnetic tape cartridge 1. In this condition,the restraining member 4, the releasing member 6, and the reel 2 aremoved to the side of the lower case 32 of the cartridge case 3 by theurging force of the urging member 5, and the opening 32 a of the centerportion of the lower case 32 is closed by the reel 2. The releasingmember 6 is in the lower most state in which the lower surface abuts theupper surface of the bottom wall 21 a of the reel hub 21, and thepushing-up portions 63 are projected so as to coincide with the toothedge position of the reel gear 24. The restraining member 4 abutting theupper surface of the releasing member 6 is also at its lowered position,and the upper end portions of the stopper protrusions 27 engage therestraining member 4, whereby rotation of the reel 2 when not being usedis restricted and forwarding of magnetic tape is inhibited.

On the other hand, when the cartridge of FIG. 3 in which the magnetictape cartridge 1 is loaded into the drive is being used, the rotatingshaft 12 of the drive-side rotation drive means 11 approaches the bottomsurface of the reel 2, and with the chucking operation, the driving gear13 meshes the reel gear 24 and moves and holds the reel 2 slightlyupward. Then, the tooth edge of the driving gear 13 abuts the lower endof the pushing-up portion 63 of there leasing member 6 and pushes upthis. As a result, the releasing member 6 moves upward against theurging force of the urging member 5, and the restraining member 4, alongwith this releasing member 6, also moves in the upward releasingdirection. This releases the engagement between the restraining gear 42and the stopper protrusions 27, whereby the reel 2 becomes free torotate. The magnetic tape is also forwarded or rewound by the drive of arecording-reproducing unit.

In the released state, the lower ends of the pushing-up portions 63 ofthe releasing member 6 are abutted, within the through holes 26 boredbetween the tooth edges of the reel gear 24, with the tooth edges of thedriving gear 13 with reliability and are pushed up, and the upwardmovement can be linearly performed with stability. Therefore, therestraining member 4 is moved by a predetermined amount of stroke,whereby the engagement between the restraining gear 42 and the stopperprotrusions 27 can be reliably released.

Next, FIGS. 5A and 5B show another embodiment, which is formed in thesame manner as the aforementioned embodiment, except that the lower endof the pushing-up portion 63 of the releasing member 6 differs.

The pushing-up portion 63, as with the aforementioned, is inserted intothe through hole 26 bored between the tooth edges 24 a of the reel gear24, and a recess 63 a engageable with the tooth edge of the driving gear13 is formed in the center portion of the lower end face of thepushing-up portion 63 which abuts the driving gear 13 of the drive-siderotation drive means 11.

When the depth of mesh between the reel gear 24 and the driving gear 13is taken to be H and the depth of mesh between the restraining gear 41and the stopper protrusion 27 (i.e., releasing height) is taken to be D(not shown), the engagement depth h of the recess 63 a of the pushing-upportion 63 with the driving gear 13 is set so that the effectivepushing-up height (H-h) of the pushing-up portion 63 is sufficientlygreater than the releasing height (D), i.e., H-h>>D, whereby it isnecessary to assure the releasing operation.

The pushing-up portion 63 in this embodiment has the recess 63 a at thelower end face. Therefore, with the chucking operation of the drive-siderotation drive means 11, the tooth edge of the driving gear 13 engagesthe recess 63 a of the pushing-up portion 63 from the non-operativecondition of FIG. 5A, as shown in FIG. 5A, and therefore, the reliableoperation of pushing up the releasing member 6 is obtained from theinitial stage of the upward movement of the driving gear 13.

FIG. 6 illustrates another embodiment of the reel gear 24. The lowerends of the opposite tooth edges 24 a of the reel gear 24 between whichthe through hole 26 is bored are removed so that they become flatshapes. The lower ends of the opposite tooth edges 24 a may be removedso that they become R shapes which form curved faces, or C shapes whichform chamfered faces, instead of becoming flat shapes.

The tooth edge 24 a of the rear gear 24 at the open end of the throughhole 26 is sharp if it is left as it is, but since it is removed so asto be low in height, as described above, formation of the metal moldbecomes easy and formability is enhanced.

Next, FIGS. 7 and 8 show other embodiments of the aforementionedreleasing member 6, in which releasing members 6 are formed by metalsheet pressing.

That is, in FIG. 7a metal plate is punched out into the developmentshape of the disk portion 61, arm portions 62, and pushing-up portions63 of the releasing member 6. The pushing-up portions 63 are formed bybending the outer extension portions of the arm portions 62 downward,and furthermore, abutting portions 63 b are formed by bending the lowerend portions of the pushing-up portions 63 inward. Note that theabutting portions 63 b may be formed in the sheet thickness of thepushing-up portion 63 without being bent.

Also, in the example of FIG. 8 the pushing-up portion 63 is bentdownward from the side portion of the outer end of the arm portion 62,and furthermore, the abutting portion 63 b is formed by bending thelower end portion of the pushing-up portion 63.

For the aforementioned releasing members 6 that are formed by metalsheet pressing, it becomes easy to assure rigidity and it is possible todesign them to a thickness such that the releasing member cannot obtainsufficient rigidity when formed from synthetic resin. Therefore,thinning of the releasing member 6 makes it easy to assure theinstallation space for the reel-rotation restraining means 10, and areduction in the size of the through hole 26 in the reel gear 24 canincrease the area of mesh of the reel 2 with the drive-side rotationdrive means 11

Next, FIGS. 9A and 9B show other embodiments of the through hole 26 andpushing-up portion 63. The inner periphery of the through hole 26 formedin the reel gear 24 of the reel 2 and the outer periphery of thepushing-up portion 63 of the releasing member 6 are constructed so thatthey contact each other through small protrusions, provided on eithersurface, which reduce the contact area.

First, in the example of FIG. 9A, the pushing-up portion 63 is square incross section and the surface is smooth, and small protrusions 26 a areformed on the inner periphery of the through hole 26 in the longitudinaldirection along the moving direction of the pushing-up portion 63. Inthe example of FIG. 9B, the through hole 26 is square in cross sectionand the inner surface is smooth, and small protrusions 63 d are formedon the surface of a pushing-up portion 63 in the form of a square bar,in the longitudinal direction along the moving direction. Theabove-mentioned small protrusions 26 a, 63 d are about a few tens μm inheight, and in the drawings, they are shown on an enlarged scale.

In FIGS. 10A and 10B there is shown a further embodiment in which thepushing-up portion 63 is formed into a round bar shape, and smallprotrusions which reduce a contact area are provided on the innerperiphery of a through hole 26 formed in the shape of a square hole.

That is, in the example of FIG. 10A, the surface of the pushing-upportion 63 in the form of a round bar is smooth, and a plurality ofsmall protrusions 26 a are formed on each surface of the inner surfacesof the through hole 26 in the longitudinal direction along the movingdirection of the pushing-up portion 63. In the example of FIG. 10B, thesurface of the pushing-up portion 63 in the form of a round bar issmooth, and a small protrusion 26 a is formed in the center portion ofeach surface of the inner surfaces of the through hole 26 in thelongitudinal direction along the moving direction of the pushing-upportion 63. Note that small protrusions which reduce a contact area maybe provided on the surface of the pushing-up portion 63 in the form of around bar. In addition, the through hole 26 may be formed into the shapeof a round hole.

In the movement of the reel-rotation restraining means 10 in thisexample from the restrained state to the released state, or the movementfrom the released state to the restrained state, the outer periphery ofthe pushing-up portion 63 of the releasing member 6 and the innerperiphery of the through hole 26 of the reel 2 are in contact with eachother through small protrusions 26 a or 26 b which reduce the contactarea, and therefore, the frictional resistance becomes smaller andstable movement of the pushing-up portion 63 is reliably performed.

Next, FIG. 11 is a sectional view of a magnetic tape cartridge ofanother embodiment in the non-operative condition, FIG. 12 an explodedperspective view of the essential parts, and FIG. 13a sectional view ofthe essential parts in the operative condition.

The basic structure and operation of a reel 2, a cartridge case 3,reel-rotation restraining means 10, etc., of a magnetic tape cartridge 1in this embodiment are the same as the aforementioned embodiment, andthe same reference numerals will be applied to the same parts to omit adescription thereof.

Note that three pairs of two stopper protrusions 27 are stood up in theupper surface of the bottom wall 21 a of the reel 2 at regular intervalson a circle at positions different in phase from through holes 26, theupper end of each stopper protrusion 27 being formed into a plurality ofgear teeth. Note that three or more through holes 26 and three or morestopper protrusions 27 may be disposed, and the upper end of the stopperprotrusion 27 may be formed into a single gear tooth. In the reel 2shown in FIG. 2, only the part of the bottom wall 21 a cut away from thereel 2 is shown.

In addition, the releasing member 6 of the reel-rotation restrainingmeans 10 is provided on the lower surfaces near the vertexes of agenerally triangular plate base 61 with pushing-up portions 63 in theform of a column extending in the up-and-down direction, respectively.Between the pushing-up portions 63, the stopper protrusions 27 arepositioned outside the plate base 61. Note that the pushing-up portion63 may be formed into the shape of a square pillar, an ellipticcylinder, etc.

Also, in the reel 2, guide members 28 are installed for guiding part ofthe releasing member 6 in an inserting direction when the pushing-upportions 63 of the releasing member 6 are inserted into the throughholes26. The guide members 28, as shown in FIGS. 16 through 18, are formedwith two guide ribs, extending in the up-and-down direction (directionof inserting the pushing-up portion 63), which guide both cornerportions of each vertex of the generally triangular plate base 61 of thereleasing member 6 to the inner wall of the reel hub 21 of the reel 2near the through hole 26 formed in the reel gear 24.

The height H1 (refer to FIG. 16) of the guide member 28 (guide rib) isformed greater than the height h1 of the pushing-up portion 63 so thatwhen the pushing-up portion 63 is inserted into the through hole 26downward, the plate base 61 is guided before the lower end portion ofthe pushing-up portion 63 reaches the upper open end of the through hole26. In addition, the circumferential edge of the upper open end of thethrough hole 26 is formed into a taper face 26 b so that the lower endof the pushing-up portion 63 is guided into the through hole 26.

If holding of the releasing member 6 is released and drops after eachvertex of the plate base 61 is positioned by the guide member 28 so thateach pushing-up portion 63 of the releasing member 6 is above eachthrough hole 26, the pushing-up portion 63 is moved in the insertingdirection and inserted into the through hole 26 by the guide of theguide member 28 in the inserting direction, whereby the releasing member6 is assembled into the reel 2.

Note that for assembling of the magnetic tape cartridge 1, the lowercase 32 is placed facing upward, and the reel 2 is placed on this.Subsequently, the releasing member 6 is installed while being guided bythe guide members 28, and the restraining member 4 and the urging member5 are placed on the member 6. Then, the upper case 31 is placed, andthereafter, the top and bottom are reversed and screws are tightenedthrough the side of the lower case 32, whereby assembling is completed.

While, in this embodiment, the guide members 28 are formed in the innerwall of the reel hub 21, the installation position is not limited tothis. At positions where the guide members 28 do not interfere with therestraining member 4, the guide members 28 may be projected from thebottom wall 21 a of the reel 2 so that part of the releasing member 6 isguided in the inserting direction of the pushing-up portion 63. Inaddition, the through holes 26 may be provided in the radially innerside from the reel gear 24.

According to this embodiment, the positioning of the pushing-up portions63 in inserting the pushing-up portions 63 of the releasing member 6into the through holes, and the assembling of the reel 2 and thereleasing member 6 through guiding of the movement in the insertingdirection, can be easily performed by providing the guide members 28 inthe reel 2. As a result, assembling of the magnetic tape cartridge 1 asa whole can be efficiently performed.

Particularly, if the pushing-up portions 63 of the releasing member 6are inserted into the through holes 26 bored in the reel gear 24provided in the reel 2 and the lower ends of the pushing-up portions 63can abut the driving gear 13, and if the guide members 28 (guide ribs)extending in the inserting direction of the pushing-up portion 63 areprovided in the inner wall of the reel 2 near the through holes 26, theguide members 28 can be formed without interfering with other componentssuch as the restraining member 4, etc., and guiding of the releasingmember 6 at the time of assembling can be satisfactorily performed nearthe through holes 26.

Next, FIG. 17 is a sectional view of a magnetic tape cartridge of stillanother embodiment in the non-operative condition, FIG. 18 is anexploded perspective view of the essential parts, FIG. 19 is a sectionalview of the essential parts in the operative condition, and FIG. 20 is aplan view of a releasing member in the assembled state.

The basic structure and operation of a reel 2, a cartridge case 3,reel-rotation restraining means 10, etc., of a magnetic tape cartridge 1in this embodiment are the same as the aforementioned embodiment, andthe same reference numerals will be applied to the same parts to omit adescription thereof.

The releasing member 6 of the reel-rotation restraining means 10 isprovided on the lower surfaces near the vertexes of a generallytriangular plate base 61 with pushing-up portions 63 (leg portions) inthe form of a column extending in the up-and-down direction,respectively. The base 61 is formed integrally with the pushing-upportions 63 by high-rigidity resin material, while at the center portionof the upper surface a sliding-contact portion 64 which contacts thecenter portion of the lower surface of the restraining member 4 isformed with a separate member having a low friction characteristic andis rigidly attached integrally to the base 61. The center portion of thelower surface of the disc portion 41 of the restraining member 4 isformed into a convex shape and is pushed against the sliding-contactportion 64.

The sliding-contact portion 64, as shown in FIG. 21, is provided by aresin molded product in the form of a disk block and is rigidly attachedwithin the recess of the base 61, with the upper surface projected fromthe upper surface of the base 61.

As high-rigidity resins for forming the base 61 of the releasing member6, there are, for example, polycarbonate (PC) or PC doped with glassfiber, ABS resin doped with glass fiber, etc. Also, as low-frictioncharacteristic materials for the sliding-contact portion 64, there arepolyoxymethylene (POM), nylon dopped with molybdenum disulfide,polytetrafluoroethylene (PTFE), etc.

FIG. 22 illustrates another embodiment of the sliding-contact portion 64of the releasing member 6. This sliding-contact portion 64 is formed byfixedly attaching a separate member, formed into a tape-like shape,which has a low friction characteristic, at a flat center position ofthe base 6.

Also, in the released state in the reel-rotation restraining means 10,the pushing-up portions 63 of the lower ends of the releasing member 6are pushed upward by the driving gear 13, while the urging force of theurging member 5 acts downward through the restraining member 4 andtherefore bending deformation will easily develop in the base 61.However, since this base 61 is molded with high-rigidity resin, thebending deformation becomes smaller. Therefore, the pushing-up portion63 can move linearly into and out of the through hole 26 with stabilitywithout contacting one side of the through hole 26, and the engagementof the restraining gear 41 and the stopper protrusions 27 can bereliably released by moving the restraining member 4 by a predeterminedamount of stroke. In addition, because the thickness of the releasingmember 6 can be reduced, an amount of stroke for movement can besufficiently assured.

On the other hand, if the reel 2 is rotated by forwarding or rewindingthe magnetic tape with the drive unit of the recording-reproducing unit,the releasing member 6 rotates integrally with the reel 2, but therestraining member 4 does not rotate because it is in a state lockedintegrally to the side of the cartridge case 3. The releasing member 6rotates and slides in a low friction or low worn state with respect tothe restraining member 4 through the sliding-contact portion 64 having alow friction characteristic. This reduces the rotation resistance of thereel 2 and enhances the wear-resisting property, whereby the occurrenceof powder due to wear can also be reduced.

According to this embodiment such as the aforementioned, the base 61 ofthe releasing member 6 is molded with high-rigidity resin material, andthe sliding-contact portion 64 contacting the restraining member 4 isformed with a separate member having a low friction characteristic.Therefore, the rigidity of the releasing member 6 is enhanced and thebending deformation is reduced. Since stable movement of the releasingmember 6 is performed, the restraining member 4 can be reliably releasedwith a predetermined amount of movement, and the operational reliabilityof the reel-rotation restraining means 10 can be assured. In addition,the friction and wear between the sliding-contact portions of both arereduced, and because of a reduction in the resistance to driving, stablerotation of the reel 2 can be performed. The occurrence of powder due towear is reduced, whereby the reliability in recording-reproducingperformance can be assured. Thus, the releasing member 6 is alsosuitable for mass production.

That is, the releasing member 6 requires high rigidity and a lowfriction characteristic. However, if it is provided by an integral resinmolded product, there is no resin material meeting both requirements,and even if it did exist, it would be a special and expensive materialand will not be suitable for mass production.

Next, FIG. 23 is a sectional view of a magnetic tape cartridge of afurther embodiment in the non-operative condition, FIG. 24 is anexploded perspective view of the essential parts, and FIG. 25 is asectional view of the essential parts in the operative condition.

The basic structure and operation of a reel 2, a is cartridge case 3,reel-rotation restraining means 10, etc., of a magnetic tape cartridge 1in this embodiment are the same as the aforementioned embodiment, andthe same reference numerals will be applied to the same parts to omit adescription thereof.

FIG. 26A is a diagram showing how the restraining member 4 of thereel-rotation restraining means 10 is molded by injection molding, andFIG. 26B is an enlarged view of the essential part A in FIG. 26A. Therestraining member 4 is molded by injecting resin into a space formed bya stationary metal mold 71 and a movable metal mold 72 through a gatefrom a runner 73. At this time, the runner 73 is connected to aprotruding portion 43, formed at the rotation center position of thereel 2 on the opposite surface of the restraining member 4 from thesurface which slides on the releasing member 6, and when the movablemetal mold 72 is moved in order to take out a molded product aftermolding, the runner 73 is separated from the restraining member 4 and agate trace 46 is formed.

FIG. 27A is a diagram showing how the releasing member 6 is molded byinjection molding, and FIG. 27B is an enlarged view of the essentialpart B in FIG. 27A. The releasing member 6 is molded by injecting resininto a space formed by a stationary metal mold 74 and a movable metalmold 75 through a gate from a runner 76. At this time, the runner 76 isconnected at the rotation center position of the reel 2 to the oppositesurface of the releasing member 6 from the surface which slides on therestraining member 4, and when the movable metal mold 75 is moved inorder to take out a molded product after molding, the runner 76 isseparated from the releasing member 6 and a gate trace 67 is formed.

Thus, by providing the gate traces 46 and 67, for injection molding, onthe sliding surfaces of the restraining member 4 and the releasingmember 6 in the vicinity of the center of rotation of the reel 2, thereis no possibility that when the restraining member 4 and the releasingmember 6 slide on each other, the sliding resistance between therestraining member 4 and the releasing member 6 will increase and powderdue to wear will occur. In addition, because the gate traces 46 and 67are provided in the vicinity of the rotation center, the flow of resinwithin the metal molds 71, 72, 74, and 75 becomes approximately uniform.With this uniformity, there is no possibility that the dimensionalprecision of the restraining member 4 and releasing member 6 will bedeteriorated, and in addition, the restraining member 4 and thereleasing member 6 can be manufactured satisfactorily in terms ofappearance and strength.

Note that while, in the above-mentioned embodiment, the gate traces 46and 67 are provided at the rotation center positions of the reel 2 onthe restraining member 4 and the releasing member 6, there is no problemeven if they are shifted slightly from the rotation center positions, ifthey are formed on the surfaces of the restraining member 4 and thereleasing member 6 opposite to the sliding surfaces of the members 4, 6.

In addition, although, in the above-mentioned embodiment, in both of therestraining member 4 and the releasing member 6 the gate traces 46 and67 are formed on the surfaces of the members 4 and 6 opposite from thesliding surfaces thereof, the gate trace may be formed on the surface ofeither the restraining member 4 or the releasing member 6 opposite tothe sliding surface.

Furthermore, in the above-mentioned embodiment, while the releasingmember 6 is injection-molded as shown in FIG. 27A, the pushing-upportions 63 of the releasing member 6 need to be stood up in a directionperpendicular to the plate base 61, because they are inserted into thethrough holes 26 and moved. However, there is a possibility that thepushing-up portions 61 cannot be precisely formed, because the platebase 61 will warp due to sinkmarks in the resin which are formed whenmolding the releasing member 6 by injection molding. In addition, as thegate trace 67 and the three pushing-up portions 63 are formed on theside of the stationary metal mold 74, as shown in FIG. 27A, there is aproblem that (1) the sliding resistance between the releasing member 6and the stationary metal mold 74 will become greater, (2) the releasingmember 6 will be pulled toward the side of the stationary metal meld 74when the stationary metal mold 74 and the movable metal mold 75 areopened, and (3) a molded product cannot be taken out smoothly from themetal molds 74 and 75.

Because of this, it is preferable to form a bore 6 a to such an extentthat it will reduce the wall thickness of the pushing-up portion 63, ata position, corresponding to the pushing-up portion 63, on the sideopposite to the movable metal mold 75 of the releasing member 6. Thatis, a pin-shaped protruding portion 75 a is formed at a position on themovable metal mold 75 which corresponds to the pushing-up portion 63,and the bore 6 a is formed in the releasing member 6 when molding thereleasing member 6 by injection molding. Since the position on thereleasing member 6 corresponding to the pushing-up portion 63 is awayfrom the gate, there is significant shrinkage when the resin hardens.Therefore, when the releasing member 6 hardens within the metal molds 74and 75, the bore 6 a shrinks and the holding force of the protrudingportion 75 a of the movable metal mold 75 develops. This prevents thereleasing member 6 from being pulled by the stationary metal mold 74when releasing the metal molds 74 and 75, making it possible to smoothlyrelease the metal molds 74 and 75 and accordingly take-out a moldedproduct.

In addition, sinkmarks in the resin can be prevented by making the wallthickness of the pushing-up portion 63 uniform. This can prevent thefall of the pushing-up portions 63 during molding. As a result, thedimensional precision of the pushing-up portion 63 can be enhanced.

According to this embodiment as described above, the gate traces 67 and46 for injection molding are provided near the centers of rotation ofthe reel 2 on the surfaces of the restraining member 4 and the releasingmember 6 opposite from the sliding surfaces thereof. Therefore, there isno possibility that with irregularities on the gate traces, the slidingresistance between the restraining member 4 and the releasing member 6will increase and powder due to wear will occur. In addition, becausethe gate traces 46 and 67 are provided in the vicinity of the rotationcenter of the reel 2, the flow of resin within the metal molds 71, 72,74, and 75 becomes approximately uniform. This uniform flow prevents thedeterioration of the dimensional precision of the restraining member 4and releasing member 6 and also makes it possible to manufacture therestraining member 4 and the releasing member 6 satisfactorily from thepoint of view in appearance and strength.

Next, FIG. 29 is a sectional view of a magnetic tape cartridge of afurther embodiment in the non-operative condition, FIG. 30 an explodedperspective view of the essential parts, FIG. 31 a sectional view of theessential parts in the operative condition, and FIG. 32a plan view of areleasing member in the assembled state.

The basic structure and operation of a reel 2, a cartridge case 3,reel-rotation restraining means 10, etc., of a magnetic tape cartridge 1in this embodiment are the same as the aforementioned embodiment, andthe same reference numerals will be applied to the same parts to omit adescription thereof.

The releasing member 6 of the reel-rotation restraining means 10 isprovided on the lower surfaces near the vertices of a generallytriangular metal plate base 61 with pushing-up portions 63 (legportions) in the form of a column extending in the up-and-downdirection, respectively.

The pushing-up portion 63 is formed with a metal processed product or aresin molded product, and as shown in FIG. 33, the corner portions ofthe lower end are chamfered so that no edges are formed. The upper endportion of this pushing-up portion 63 is provided with an attachingportion 63 f that consists of a bar-shaped screw. The attaching portion63 f is screwed into a screw hole 61 a formed in each vertex portion ofthe base 61 and is rigidly attached.

In addition, FIGS. 34A and 34B show other embodiments of the rigidstructure for attaching the pushing-up portion 63 of the releasingmember 63 to the base 61. In FIG. 34A, a snap-type attaching portion 63g is formed integrally in the upper end portion of a resin pushing-upportion 63, and the attaching portion 63 g is inserted into a steppedattaching hole 61 b formed in each vertex portion of the base 61 and isrigidly attached. In FIG. 34B, a metal clip-type attaching portion 63 his formed integrally in the upper end portion of the resin pushing-upportion 63, and the attaching portion 63 h is inserted into a attachinghale 61 c formed in each vertex portion of the base 61 and is rigidlyattached.

Besides, the rigid attachment of the pushing-up portion 63 to the base61 can adopt known methods such as press-fit, caulking (heat, welding),shrinkage fit, etc. It is preferable that for the attaching portions 63f to 63 h in the pushing-up portions 63, the attaching portion in themetal pushing-up portion be formed by cutting, or by rigidly attaching aseparate component. It is also preferable that for the resin pushing-upportion, the resin attaching portion be provided integrally by molding,or rigidly attached by welding, etc., or the metal attaching portion beprovided by insert molding.

Next, FIG. 35 shows that in the case of the resin pushing-up portion 63,metal material 63 k is rigidly attached to a surface of the lower endportion of the pushing-up portion 63 which contacts the driving gear 13.In this embodiment, the wear-resisting property of the resin pushing-upportion 63, which is contacted by the driving gear 13 made of metal, isenhanced. The metal material 63 k is provided by attachment of a metalplate (metal foil), insert molding, etc.

In the released state in the reel-rotation restraining means 10, thepushing-up portions 63 of the lower ends of the releasing member 6 arepushed upward by the driving gear 13, while the urging force of theurging member 5 acts downward through the restraining member 4 andtherefore bending deformation will easily develop in the base 61.However, since this base 61 is formed from metal, bending deformationbecomes smaller. The pushing-up portion 63 can also be preciselyattached by a separate member. Therefore, the pushing-up portion 63 canlinearly move into and out of the through hole 26 with stability withoutcontacting one side of the through hole 26, and the engagement of therestraining gear 41 and the stopper protrusions 27 can be reliablyreleased by moving the restraining member 4 by a predetermined amount ofstroke. In addition, because the thickness of the releasing member 6 canbe reduced, an amount of stroke for movement can be sufficientlyassured. Furthermore, the driving gear 13 is capable of smoothlyabutting the pushing-up portion 63, and there is no possibility that thedriving gear 13 will be caught on the edge portion.

Note that if the driving gear 13 is made of metal and the tooth edge issharp, it will wear the pushing-up portion 63 when it abuts thepushing-up portion 63, and therefore, the driving gear 13 made of metalwill be disadvantageous in terms of durability. Because of this, it ispreferable to form the tooth edge of the driving gear 13 into a curvedsurface, as shown in FIGS. 36, 37A, and 37B.

In FIGS. 36, 37A, and 37B, the tooth edge portion 13 a of the drivinggear 13, as a shape of facilitating metal cutting of the driving gear13, is formed so that the edge is flat at the radially outer portion andsharp and low in height at the radially inner portion, the angles of thetooth side faces differ at both sides, and the tooth groove 13 b isformed wide. In the form shown in FIG. 37A, the edge of the tooth edgeportion 13 a on the radially inner side which becomes sharp is formedinto a curved surface (R-surface) by chamfering, whereby damage to thereel gear 24 which meshes with this driving gear 13 and damage to thelower end of the pushing-up portion 63 of the releasing member 6, whichwill occur when they abut each other, are alleviated. Similarly, in theform of FIG. 37B, the radially outer flat edge of the tooth edge portion13 a, as with the radially inner side, is formed into a curved surface(R-surface) by chamfering.

Furthermore, in the case where the reel gear 24 formed in the reel 2 hasthe same gear shape as the driving gear 13, the tooth edge may likewisebe formed into a curved surface (R-surface) by chamfering.

FIGS. 38 and 39 show a gear shape example of the reel gear 24. The topof the tooth edge portion 24 a is formed into a flat surface at theradially inner and outer portions so that a sharp edge portion is notformed. The angles of the tooth side faces of this reel gear 24 differat both sides, the tooth groove 24 b is formed wide and deep, and theflat face of the tooth edge portion 24 b is formed so that the radiallyinner and outer widths are approximately the same. This can increase thestrength of the reel gear 24 made of resin and prevent the tooth frombreaking when it meshes the driving gear 13 made of metal. Note that thedriving gear 13 may likewise be formed so that the top of the tooth edgeportion is flat.

According to this embodiment such as the aforementioned, the base 61 ofthe releasing member 6 is made of metal, while the pushing-up portion 63is formed as a separate body and rigidly attached to the base 91.Therefore, the releasing member 6 is enhanced in dimensional precisionand rigidity, and the bending deformation is reduced. The sliding motionof the pushing-up portion 63 within the through hole 26 can also beassured. Since stable movement of the releasing member 6 can beperformed, the restraining member 4 can be reliably released with apredetermined amount of movement, and the operational reliability of thereel-rotation restraining means 10 can be assured.

In addition, if at least the lower end portion of the pushing-up portion63 is made of metal, the durability to the pressing action on the lowerend of this pushing-up portion is enhanced.

Next, an embodiment related to the reel and the manufacturing methodwill be described. FIG. 40A shows a bottom view of the reel plate 25(metal plate) of the bottom center of the reel 2, and FIG. 40B shows asectional view of the molded state.

The reel plate 25 is formed into an annular shape having a center hole25 a. In the molded state with the reel plate 25 inserted into thebottom wall 21 a of the reel 2, the part of the center hole 25 a isclosed by the resin of the bottom wall 21 a, and so as the reel gear 24is provided to project from the-plate surface.

Injection molding of the reel 2, as shown in FIG. 40B, is performed byinjecting resin into a cavity formed by a stationary metal mold 71 and amovable metal mold 72 through the gate 77 a of a gate bush 77. The gatebush 77 is disposed in the center portion of the stationary metal mold71, and a hold member 78 to hold the inner peripheral surface of thereel plate 25 is disposed on the outer periphery of the gate bush 77.The hold member 78 is tubular in cross section and provided at the lowerend with a ring protrusion 78 a. The inner peripheral surface of thecenter hole 25 a of the reel plate 25 is fitted onto the outerperipheral surface of the ring protrusion 78 a. This reel plate 25 isheld with the plate surface being in intimate contact with an innersurface which is at a predetermined position on the metal mold 71. Inthis manner, the movable metal mold 72 is closed, and resin is injected.

After molding, the hold trace 2 lb of the ring protrusion 78 a of thehold member 78 is formed as a ring groove in the reel 2, at the part ofthe bottom wall 21 a closing the center hole 25 a of the reel plate 25.In addition, a gate trace 21 c is formed in the center portion.

If insert molding is performed with the inner peripheral surface of thecenter hole 25 a of the reel plate 25 held by the above-mentioned holdmember 78, the reel plate 25 can be prevented from moving and shiftingout of position because of the flow of resin, and therefore, the reelplate 25 can be rigidly attached at a predetermined position on the reel2. In addition, all that is required at the time of wear is to changecomponents, because the hold member 78 is formed as a member separatefrom the stationary metal mold 71 and the gate bush 77.

FIG. 41A shows another embodiment of the structure for holding the reelplate 25 and FIG. 41B the molded state. In this example, the lower endof the hold member 78 for holding the reel plate, provided in thestationary metal mold 71, has a pin structure.

That is, the hold member 78 is tubular in cross section, and three ormore hold pins 78 b (in the figure, 3 pins) project from the lower end.The outer peripheral surfaces of the hold pins 78 b abut the innerperipheral surface of the center hole 25 a of the reel plate 25, wherebythis reel plate 25 is held with the plate surface being in intimatecontact with an inner surface which is at a predetermined position onthe metal mold 71. In this way, the movable metal mold 72 is closed, andinjection molding is performed by injecting resin from the gate 77 a.

In the reel 2 after molding, three hold traces 21 d in the form of arecess are formed in the bottom wall 21 a, integrally formed inside thecenter hold 25 a of the reel plate 25, and at the center portion, a gatetrace 21 c is formed. In the holding by the hold pins 78 b, even if thehold pins 78 b are projected from the reel plate 25, the projection haslittle influence on the flow of resin injected from the gate 77 a.Therefore, the amount of projection of the hold pins 78 b may beincreased in order to enhance the function of holding the reel plate 25.

Next, FIG. 42 shows another embodiment of the metal mold. The reel plate25 placed on the stationary metal mold 71 is pressed and locked by amovable pin 79, urged by a spring 80 provided in the movable metal mold72. In this locked state, injection molding is performed by injectingresin.

This prevents the reel plates 25 from being moved by the flow of resinat the time of injection, whereby molding of the reel 2 can be performedwith the reel plate 25 attached at a predetermined position. Inaddition, although a pin hole is formed in the reel bottom wall 21 a bythe movable pin 79, it is closed by the reel plate 25 and thereforedustproof property can be assured. Note that in addition to the holdingof the reel plate 25 by the hold member 78 shown in FIG. 40B or 41B, thepressing and locking by the movable pin 79 may be performed.

FIG. 43 shows still another embodiment regarding the locking of the reelplate 25. In this example, the reel plate 25 is held in a predeterminedposition on the stationary metal mold 71 by magnetic force.

That is, a magnet 81 is disposed on the outer peripheral portion of thegate bush 77 of the stationary metal mold 25 so that it is coplanar withthe metal mold surface. The reel plate 25 is attracted and held with themagnetic force of the magnet 81, and insert molding is performed.

Next, various forms of reel plates 25, for enhancing the rigidattachment force of the reel 2 to the bottom wall 21 a, will be shown.

The reel plate 25 shown in FIG. 44A has a center hole 25 a. Also, threerigid-attachment holes 25 b are bored in the flat portion, and taperportions 25 c such as those shown-in FIG. 44B, or stepped portions 25 dsuch as those shown in FIG. 44C, are formed over the respective halfperipheries of the outer peripheral portion, the inner peripheralportion of the center hole 25 a, and the inner peripheral portion of therigid attachment hole 25 b.

The insert molding of the aforementioned reel plate 25 is performed withthe surface of FIG. 44A being in intimate contact with the inner surfaceof the stationary metal mold 71, and the taper portions 25 c or steppedportions 25 d are also filled with resin in order to enhance the rigidattachment force of the reel plate 25, whereby the disengagement of thereel plate 25 from the reel is prevented. In addition, higher rigidattachment force is obtained by boring the rigid-attachment holes 25 b.

A center hole 25 a and rigid-attachment holes 25 b (three holes) arebored, in the reel plate 25 shown in FIGS. 45A and 45B, and taperportions 25 c are formed over the respective whole peripheries of theouter peripheral portion, the inner peripheral portion of the centerhole 25 a, and the inner peripheral portion of the rigid-attachment hole25 b.

A center hole 25 a and rigid-attachment holes 25 b (six holes) arebored, in the reel plate 25 shown in FIGS. 46A and 46B, and taperportions 25 c are formed over the respective whole peripheries of theinner peripheral portions of the rigid-attachment holes 25 b. Thedirections of the taper portions 25 c are alternated on three of theholes 25 b so that both sides of the reel plate 25 become symmetrical inshape, whereby interchangeability between both sides is provided. Thiseliminates the necessity for selecting the upper or lower side of thereel plate 25 when setting it to the metal mold 71, whereby operabilityis enhanced.

An annular groove 25 e is formed in the outer peripheral surface in thereel plate 25 shown in FIGS. 47A and 47B. This groove 25 e is filledwith resin, whereby rigid attachment force increases.

Rigid attachment grooves 25 f in undercut form are formed in the surfaceof the reel plate 25, shown in FIGS. 48A and 48B, which contacts resin.The rigid attachment grooves 25 f in undercut form are filled withresin, whereby rigid attachment force increases.

Note that in the case where the rigid-attachment hole 25 b is bored inthe reel plate 25, as previously described, the gate position forinjection molding may be provided in the part of the rigid-attachmenthole 25 b.

Next, FIGS. 49 through 52 show various forms of the reel plate 25 andthe reel gear 24 formed in the outer periphery. In these forms, when themolded reel 2 is separated by the metal mold 71, the interferencebetween the gear portion metal mold for molding the reel gear 24 and thereel plate 25 is prevented.

The form shown in FIG. 49 forms a clearance (which is filled with resin)in the radial direction between the outer peripheral surface of the reelplate 25 and the inner peripheral end of the reel gear 24, therebypreventing the interference between the reel plate 25 and the gearportion metal mold when separating the mold from the plate.

The form shown in FIG. 50 forms a clearance in the height directionbetween the height position of the outer peripheral end of the reelplate 25 and the height of the tooth bottom portion of the reel gear 24,thereby preventing the aforementioned interference.

The form shown in FIG. 51 inclines the outer peripheral surface of thereel plate 25 and forms a clearance between the corner portion of theouter periphery of the reel plate 25 and the tooth bottom portion of thereel gear 24, thereby preventing the aforementioned interference.

The form shown in FIG. 52 chamfers the inner end portion of the gearportion metal mold, which molds the tooth bottom portion of the reelgear 24, and forms a clearance between the chamfered portion and theouter peripheral end of the reel plate 25, thereby preventing theaforementioned interference.

According to this embodiment, as described above, for the insert moldingof the annular reel plate 25 having the center hole 25 a at the bottomsurface of the reel 2, the hold trace 21 b or 21 d in the form of arecess, which is formed by the hold member 78 of the metal mold holdingthe reel plate 25, is formed in the reel bottom wall 21 a closing thecenter hole 25 a of the reel plate 25 with resin. Therefore, the holdingof the reel plate 25 during insert molding can be reliably performed,and desired insert molding can be performed without movement of the reelplate 25 which is caused by the pressure and flow of resin at the timeof injection molding. Also, there is no possibility that the reel plate25 in the reel 2 after molding will project, and therefore, interferencewith other components can be prevented. In addition, the center hole 25a is closed, whereby dustproof property can be easily assured.

In addition, according to the aforementioned molding method, the reelplate 25 is held during insert molding by the movable pin 79 provided inthe metal mold, or by magnetic force. Therefore, the holding of the reelplate 25 to the metal mold can be reliably performed without forming athrough hole in the molded reel 2, and the reel plate 25 can be formedintegrally at a predetermined position on the reel 2.

Next, another embodiment of the insert molded portion of the reel plate25 will be shown. FIG. 53A shows a bottom view of the reel plate 25 ofthe bottom center portion of the reel 2 and FIG. 53B a sectional view ofthe molded state.

The aforementioned reel plate is formed into an annular shape having acenter hole 25 a. In the molded state with reel plate 25 inserted intothe bottom wall 21 a of the reel 2, the part of the center hole 25 a isclosed by the resin of the bottom wall 21 a, and outside an outerperipheral surface 25 g, a clearance 21 f in the form of acircumferential groove is formed between the outer peripheral surface 25g and the reel bottom wall 21 a surrounding this. Outside the clearance21 f, a reel gear 24 is provided.

Injection molding of the reel 2, as shown in FIG. 53B, is performed byinjecting resin into a cavity formed by a stationary metal mold 71 and amovable metal mold 72 through a gate 71 b. The stationary metal mold 71is provided with a ring protrusion 71 a for holding the outer peripheralsurface of the reel plate 25. The outer peripheral surface 25 g of thereel plate 25 is fitted into the inner peripheral surface of the ringprotrusion 71 a, and this reel plate 25 is held on an inner surfacewhich is at a predetermined position on the metal mold 71. The movablemetal mold 72 is closed, and resin is injected.

In the reel 2 after molding, at the part of the bottom wall 21 a of theouter peripheral surface 25 g of the reel plate 25, a clearance 21 f inthe form of a circumferential groove, which results from the hold traceof the ring protrusion 71 a, is formed in recess form. In addition, agate trace 21 c is formed in the center portion of the bottom wall 21 athat closed the center hole 25 a.

If insert molding is performed with the outer peripheral surface 25 g ofthe reel plate 25 held by the above-mentioned ring protrusion 71 a, thereel plate 25 can be prevented from moving and shifting out of positionbecause of the flow of resin, and therefore, the reel plate 25 can berigidly attached at a predetermined position on the reel 2. In addition,because of formation of the clearance 21 f, the shrinking forceresulting from the shrinkage of resin after insert molding will not acton the outer peripheral surface 25 g and therefore deformation of thereel plate 25 can be suppressed.

FIG. 54 shows another embodiment of the reel plate 25. Reinforcementribs 25 h are formed on the upper surface of the reel plate 25 thatcontacts the reel bottom wall 21 a. These reinforcement ribs 25 h areformed by radial and ring ribs projecting from the plate surface. Notethat the lower surface of the reel plate 25 which is exposed to thebottom surface of the reel 2 has no reinforcement rib and is providedflat. Also, the form of the reinforcement rib 25 h is designed andchanged as appropriate, according to the required strength.

Such a reel plate 25 is insert-molded integrally with the reel 2, whileit is being held by the aforementioned stationary metal mold 71 (thering protrusion 71 a is not always a necessity).

According to the form shown in FIG. 54, even if the bending strength ofthe reel plate 25 increases and the shrinking force of the resin formingthe reel bottom wall 21 a after insert molding acts on the reel plate25, the deformation will be suppressed by formation of the reinforcementribs 25 h.

Next, FIG. 55 is a plan view showing another embodiment of the reel 2.As previously described, the reel plate 25 is rigidly attached to thebottom surface of the bottom wall 21 a of the reel hub 21. In thebottomwall 21 a of the reel 2 which contacts the upper surface of thereel plate 25, recesses 29 are formed and resin contacting the uppersurface of the reel plate 25 is partially removed. That is, the surfaceof the aforementioned movable metal mold 72 is molded in contact withthe reel plate 25 so that the bottom wall 21 a is in an open state atthe parts of the recesses 29 and the upper surface of the reel plate 25is exposed to the bottom surfaces of the recesses 29.

Note that in formation of the recesses 29, the aforementioned gate 71 bis located at the center portion of the reel bottom wall 21 a and it istherefore necessary to form the recesses 29 with spaces so that resininjected from this gate portion flows uniformly to each part, andparticularly so that a flow in the radial direction is not disturbed. Inaddition, the recesses 29 may be formed to reduce the wall thickness ofthe reel bottom wall 21 a.

According to the form shown in FIG. 55, the recesses 29 are formed inthe reel bottom wall 2 la contacting the reel plate 25, whereby theamount of the resin contacting the reel plate 25 is reduced and theshrinking force of the resin after insert molding becomes smaller. As aresult, deformation of the reel plate 25 can be suppressed.

According to this embodiment as described above, for the insert moldingby which the reel plate 25 for magnetic attraction is molded integrallyto the bottom surface of the reel 2, a clearance is formed between theouter peripheral surface of the reel plate 25 and the reel bottom wall21 a surrounding this. Therefore, no shrinking force acts from the outerperipheral surface to the center direction when resin after insertmolding is shrunk, deformation of the reel plate 25 can be suppressedand therefore a uniform clearance with the magnet can be assured. Withformation of the clearance 21 f in the outer periphery of the reel plate25, the reel plate 25 is held by the protrusion 71 a of the metal moldcorresponding to this clearance 21 f, whereby positioning of the reelplate 25 during insert molding can be performed with reliability anddesired insert molding can be performed without movement of the reelplate 25 that is caused by the pressure and flow of resin at the time ofinjection molding.

In addition, in the example where the reinforcement ribs 25 h areprovided on the surface of the reel plate 25 which contacts the reelbottom wall 21 a, deformation of the reel plate 25, which is caused byan increase in the strength of the reel plate and the shrinking force ofresin when shrunk after insert molding, can be suppressed and thereforea uniform clearance with the magnet can be assured.

Furthermore, in the example wherein the bottom wall 21 a of the reel 2contacting the reel plate 25 is partially removed, the shrinking forcepulling the reel plate surface in the center direction, which developsas resin shrinks after insert molding, is reduced. As a result,deformation of the reel plate 25 can be suppressed, whereby a clearancewith the magnet can be assured.

Next, an embodiment regarding formation of the tape reel will be shown.FIG. 56 is a sectional view of the reel and FIG. 57 an enlarged view ofthe essential part.

On the reel 1, a cylindrical reel hub 21 in which magnetic tape is woundon the outer peripheral surface 21, and a lower flange portion 22projecting in disk form in the radial direction from the outer peripheryof one end portion (in the figure, lower end portion) of this reel hub21, are integrally formed from synthetic resin, and an upper flangeportion 23 in the form of a disc, formed as a separate body by syntheticresin, is rigidly attached to the other end portion of the reel hub 21by an adhesive.

A disc bottom wall 21 a is continuous to the inner peripheral portion ofthe reel hub 21, and in the outside surface of this bottom wall 21 a, areel gear 24 for driving the reel 1 to rotate is formed in ring form.Furthermore, on the radially inner side from this real gear 24, a realplate 25 for magnetic attraction, made of an annular metal plate, isinserted when molded.

Moreover, in the end surface of the reel hub 21 to which the upperflange portion 23 is rigidly attached, a stepped portion 56, recessed inring form so that a portion on the side of the inner peripheral surface21 h becomes lower in height, is formed as shown in FIG. 57. Also, theend surface 56 a of the stepped portion 56 in this reel hub 21 and theend portion of the hub inner peripheral surface 21 h become adhesionsurfaces.

On the other hand, the upper flange portion 23 has a circular opening atthe central portion, and at the circumferential margin of this opening,a collar portion 57 is formed projecting in the direction perpendicularto a flange surface 23 a. As shown in FIG. 57, the corner portionbetween this collar portion 57 and the flange surface 23 a is formedinto an annular protruding portion 58 which fits on the stepped portion56 of the reel hub 21. Also, the end surface 58 a (surface parallel withthe flange surface 23 a) of the annular protruding portion 58 in thisupper flange portion 23 and the outer peripheral surface 57 a of thecollar portion 57 become adhesion surfaces.

For the adhesion between the reel hub 21 and the upper flange portion23, an adhesive is supplied in a predetermined amount to the adhesionsurface of the reel hub 21 and/or the adhesion surface of the upperflange portion 23 by supply means such as a dispenser, etc. While bothare being positioned, the collar portion 57 of the upper flange portion23 is inserted onto the inner peripheral surface 21 h of the reel hub21, and the annular protruding portion 58 is fitted and assembled on thestepped portion 56. The outer peripheral surface 57 a of the flangecollar portion 57 and the inner peripheral surface 21 h of the reel hub21 are joined at a surface parallel (or may be inclined at an angle ofabout 1 to 10°) to the axis of rotation of the reel hub 21, and the endsurface 58 a of the annular protruding portion 58 and the end surface 56a of the stepped portion 56 are joined at a surface perpendicular to therotation axis of the reel hub 21.

As the adhesive, a wide variety of adhesives are usable. However, it ispreferable to use a light hardening type adhesive, particularly anultraviolet ray hardening type adhesive or a visible light hardeningtype adhesive. In the case of this light hardening type adhesive, theadhesive is applied to an adhesion surface and is then hardened byirradiating light (ultraviolet ray, visible light) for a predeterminedtime period (e.g., 5 sec). In this manner, the adhesion process ends.

The ultraviolet ray hardening type adhesive uses, for example, a knownone which has an acryloyl group to a few acryloyl groups as a functionalgroup and also has a composition that makes a radical polymerizationreaction with a photo polymerized monomer, etc., by ultraviolet rays andis bridged and polymerized. For instance, there are 3-BONDs 3062, 3055,3065 (3-Bond), ALONETIGHTs BU-130U, BU-230U, BU-249U (Toagosei), etc.The aforementioned ultraviolet ray hardening type adhesive may beequipped with a given hardening property such as anaerobic hardening,primer hardening, etc. These adhesives are hardened in a few seconds totens of seconds when irradiated with ultraviolet rays of wavelength 200to 400 nm. In this case it is preferred to mold the upper flange portion23 or reel hub 21 with transparent resin such as polycarbonate(PC),polystyrene(PS), etc. However, resin does not always need to betransparent, because there is a type in which adhesion surfaces arecombined together after irradiation of ultraviolet rays.

As a visible light hardening type adhesive, there are ALONE-TIGHTsVL-1303, VL-2303, VL-5303, etc. These can be used for adhesive even whenthe upper flange portion 23 or reel hub 21 is semitransparent orslightly colored.

In the above-mentioned embodiments, in order to enhance the adhesivestrength of an adhesive, at least one of the adhesion surfaces in theadhesion portion between the end surface 56 a of the stepped portion 56of the reel hub 21 and the end surface 58 a of the annular protrudingportion 58 in the upper flange portion 23 and the adhesion portionbetween the end portion of the hub inner peripheral surface 21 h and theouter peripheral surface 57 a of the collar portion 57 of the upperflange portion 23 is roughened as occasion demands. Roughening of thisadhesion surface is obtained by roughening the surface of theadhesion-surface molding portion of the metal mold for the reel hub 21or upper flange portion 23, and it is preferable that the surfaceroughness be 1 μm or more in terms of Rz.

According to this embodiment, the reel hub 21 and the upper flangeportion 23 are joined by an adhesive. As a consequence, adhesion can beuniformly performed over the whole periphery without giving rise todeformation in the upper flange portion 23. The reel 1 after rigidattachment can be formed with dimensional precision corresponding tomolding precision. The upper flange portion 23 can be rigidly attachedperpendicular to the rotation axis of the reel hub 21. When this reel 1is being rotated to forward or rewind magnetic tape, the deflection ofthe rotation of the upper flange portion 23 is small and lateralfluctuation in magnetic tape being traveled is also small. Therefore,satisfactory positional precision is obtained, an influence on recordingand reproducing characteristics is small, and in addition, it becomespossible to meet the high-density requirement of the magnetic tapecartridge.

In addition, the adhesion between the reel hub 21 and the upper flangeportion 23 is performed at a position away from the outer peripheralsurface 21 g of the reel hub 21, and on the radially inner side from thestepped portion 56. As a result, the adhesive is prevented fromoverflowing from the adhesion surface to the part of the outerperipheral surface 21 g, and the influence of the adhesive on themagnetic tape that is wound on this outer peripheral surface 21 g can beeliminated.

Furthermore, if the adhesion surface is roughened, the adhesion area towhich an adhesive is applied is increased and the adhesive strength isenhanced. As a result, the adhesion between the reel hub 21 and theupper flange portion 23 can be more firmly performed, and the adhesionsurface can endure an increase in the winding tension without increasingthe adhesion area.

Although, in the above-mentioned embodiment, adhesion is performed attwo surfaces perpendicular to each other in order to obtain highadhesive strength, at least the adhesion between the outer peripheralsurface 57 a of the collar portion and the hub inner peripheral surface21 h is necessary.

FIGS. 58 and 59 show a reel 2 according to another embodiment. Thisembodiment differs in the shape of the adhesion portion, and the otherparts are provided in the same way as FIG. 56.

In the end surface of the reel hub 21 to which the upper flange portion23 is rigidly attached, an annular recess 59 is formed so that a portionon the side of the outer peripheral surface 21 g becomes lower inheight, as shown in FIG. 59. The end surface 59 a and peripheral surface59 b of this recess 59 become adhesion surfaces. On the other hand, theupper flange portion 23 is in the form of a disc with a circular openingat the central portion, and as shown in FIG. 59, the inner peripheralsurface 23 b and the radially inner portion of the inner flange surface23 a become adhesion surfaces.

For the adhesion between the reel hub 21 and the upper flange portion23, an adhesive is supplied in a predetermined amount to the adhesionsurface of the reel hub 21 and/or the adhesion surface of the upperflange portion 23 by supply means such as a dispenser, etc. While bothare being positioned, the inner peripheral portion of the upper flangeportion 23 is fitted and assembled on the recess 59 of the reel hub 21.The inner peripheral surface 23 b of the upper flange portion 23 and theperipheral surface of the recess 59 b of the reel hub 21 are adhered ata surface parallel to the axis of rotation of the reel hub 21, and theend surface 59 a of the recess of the reel hub 21 and the radially innerportion of the flange surface 23 a are adhered at a surfaceperpendicular to the rotation axis of the reel hub 21.

In this embodiment, as with the above-mentioned embodiment, at least oneof the adhesion surfaces in the adhesion portion between the recess endsurface 59 a of the reel hub 21 and the radially inner flange surface 23a of the upper flange portion 23 and the adhesion portion between therecess peripheral surface 59 b of the reel hub 21 and the innerperipheral surface 23 b of the upper flange portion 23 is roughened asoccasion demands, thereby increasing the adhesive strength of theadhesive.

According to this embodiment, as with the aforementioned embodiment, thereel hub 21 and the upper flange portion 23 are joined by an adhesive.As a consequence, the reel hub 21 and the upper flange portion 23 can beuniformly adhered over the whole periphery without giving rise todeformation in the upper flange portion 23. The deflection of therotation of the upper flange portion 23 is small and lateral fluctuationin magnetic tape being transported is also small. Furthermore, itbecomes possible to meet the high-density requirement of the magnetictape cartridge.

In addition, high adhesive strength is obtained by joining the reel hub21 and the upper flange portion 23 at two surfaces perpendicular to eachother. Furthermore, a stepped portion may be formed in the recess 59 ofthe reel hub 21.

Note that in both embodiments, the adhesion surface, in addition tobeing provided continuously on the whole periphery, may be formed in adiscontinuous shape having a partial groove partially. In this case, anexcess of adhesive can be more effectively prevented from flowing in thegroove and overflowing from the adhesion surface to the outside.

According to this embodiment as described above, the upper flangeportion 23 in the form of a disc is rigidly attached by an adhesive tothe end portion of the cylindrical reel hub 21 in which tape is wound onthe outer peripheral surface 21 g. As a result, the upper flange portion23 is rigidly attached so that it is at a right angle to the rotationaxis and deformation does not develop, whereby satisfactory dimensionalprecision can be obtained. By making the lateral deflection of woundtape smaller, even for resin molded products it becomes possibleto-sufficiently meet the enhanced recording density and recordingprecision requirements.

If a light hardening type adhesive, particularly an ultraviolet rayhardening type adhesive is used as the aforementioned adhesive, massproduction and process simplification can be achieved by a reduction inthe hardening time.

Furthermore, by employing an adhesive it is also possible to combine thereel hub 21 and the upper flange 23, made of resin, which can not bewelded by ultrasonic welding. Also, in ultraviolet welding, the flatnessof the reel hub 21 and the cylindricality of the lower flange portion 22are reduced due to an unevenness in wall thickness between the reel hub21 and the lower flange portion 22 integrally formed in order to assureweld surfaces, but uniform wall-thickness molding becomes possible. As aresult, an enhancement in the molding precision of the reel hub 21 isachieved and the reel 2 with higher precision is obtained.

In addition, all of the contents of Japanese Patent Application Nos.10(1998)-158784, 10(1998)-202497, 10(1998)158786, 10(1998)-160387,10(1998)-236935, 10(1998)-202498, 10(1998)-245308, 10(1998)-344984 and10(1998)-217432 are incorporated into this specification by reference.

What is claimed is:
 1. A magnetic tape cartridge, for rotatably housingwithin a cartridge case a single reel having magnetic tape woundthereon, comprising reel-rotation restraining means for allowingrotation of said reel when being used and restricting said rotation whennot being used; wherein said reel-rotation restraining means has arestraining member for restricting rotation of said reel by movingtoward or away from said reel, an urging member for urging saidrestraining member in a restraining direction, and a releasing memberfor moving said restraining member in a releasing direction, by rotatingintegrally with said reel and moving according to a chucking operationof drive-side rotation drive means; said reel is provided with a reelgear which meshes with a driving gear of said drive-side rotation drivemeans, and a pushing-up portion formed in part of said releasing memberis provided so that a distal end thereof can abut said driving gearthrough a through hole provided in said reel gear; and gate traces forinjection molding are provided near centers of rotation of saidrestraining member and said releasing member, wherein, in the releasingmember which has the pushing-up portion and is formed by injectionmolding, such a bore which reduces a wall thickness of said pushing-upportion is formed in the interior of said pushing-up portion.
 2. Amagnetic tape cartridge, for rotatably housing within a cartridge case asingle reel having magnetic tape wound thereon, comprising: areel-rotation restraining device that allows rotation of said reel whenbeing used and restricting said rotation when not being used; whereinsaid reel-rotation restraining device has a restraining member thatrestricts rotation of said reel by moving toward or away from said reel,an urging member that urges said restraining member in a restrainingdirection, and a releasing member that moves said restraining member ina releasing direction, by rotating integrally with said reel and movingaccording to a chucking operation of a drive-side rotation drive device;said reel is provided with a reel gear which meshes with a driving gearof said drive-side rotation drive device, and a pushing-up portionformed in part of said releasing member is provided so that a distal endthereof can abut said driving gear through a through hole provided insaid reel gear; and gate traces for injection molding are provided nearcenters of rotation of said restraining member and said releasingmember, wherein, in the releasing member which has the pushing-upportion and is formed by injection molding, such a bore which reduces awall thickness of said pushing-up portion is formed in the interior ofsaid rushing-up portion.